This document generally relates to wireless communication systems. Early mobile or wireless communication systems, now referred to as first generation (1G), used analog technology called frequency division multiple access (FDMA) to deliver a radio-based voice channel to a mobile telephone user. In the late 1980s, second generation (2G) systems were deployed using digital technologies. The first U.S. system used time division multiple access (TDMA). In the early 1990s, TDMA technology was used to introduce the Global System for Mobile Communication (GSM) to Europe. In the mid 1990s, code division multiple access (CDMA) became the second type of digital 2G system, with the U.S. introduction of Interim Standard-95 (IS-95).
Wideband CDMA (WCDMA) is a transmission technology for 3G (third generation) Universal Mobile Telecommunications System (UMTS) mobile or wireless communication. WCDMA systems support voice and data transmission with variable data rates in wireless communication channels such as random access channels, paging channels, broadcast channels, etc. WCDMA systems contain one or several radio frequency carriers. Each radio frequency carrier contains a number of spreading codes which may be allocated to provide different data rates to satisfy different mobile user requirements.
WCDMA systems often utilize transport channels which may be mapped to physical channels. The physical layer/channel (layer 1) is the lowest layer in the OSI Reference Model and it supports functions used for the transmission of bit streams on the physical medium. The physical layer subsequently provides data transport services to higher layers of the wireless communication system. Characteristics of a transport channel are defined by its transport format (or format set), specifying the physical layer processing to be applied to the transport channel in question, such as convolutional channel coding and interleaving, and any service-specific rate matching as may be needed. Transport channels may represent services offered by Layer 1 to the higher layers.
Exemplary transport channels include: a) common transport channels such as BCH (broadcast channel, often used as a downlink (DL) transport channel to broadcast system and/or cell specific information), FACH (forward access channel), PCH (paging channel), RACH (random access channel), CPCH (common packet channel), and DSCH (downlink shared channel), and b) dedicated channels (DCH) which may be used on the uplink or downlink.
TD-SCDMA (Time Division Synchronous Code Division Multiple Access) is also a transmission technology for 3G (third generation) Universal Mobile Telecommunications System (UMTS) mobile or wireless communication. TD-SCDMA uses time domain duplexing in combination with code domain multiple access techniques to support both symmetrical and asymmetrical traffic.
High speed downlink packet access (HSDPA) is an important feature of Release 5 of the third Generation Partnership Project (3GPP) specification and represents the first step in the evolution of TD-SCDMA toward high data rates. More specifically, HSDPA is a UMTS enhancement to provide increased downlink data rates that is defined in Release 5 of the UMTS specifications. The HSDPA is expected to increase system capacity, reduce roundtrip delay and increase peak data rates to more than 2.0 megabits per second. A new shared channel called high speed downlink shared channel (HS-DSCH) has been introduced to support the above goals.
In traditional communication systems, the baseband receiver includes two main components: an inner receiver, also known as an equalizer or a chip rate processor, which mitigates the effects of multi-path and interference, and an outer receiver which performs channel decoding and other symbol rate processing.